The proposed project is a follow-up of middle-aged male participants in an 18-month exercise intervention (The Cooperative Study on Physical Activity and Cardiovascular Disease, 1966-68) to (1) determine what, if any, lasting improvements in health practices and coronary heart disease (CHD) risk factor status accrued; (2) establish whether individuals who permanently improved their health practices differ from those who did not by virtue of age, initial health status, or anthropomorphic, physiological, psychological or demographic factors; and (3) examine the relationship between chronic physical activity level and age-related changes in structure and function. Subjects will be recruited from participants in the original study as follows: random sample (RS) of 85 from 719 men then at low risk for CHD; RS of 45 from 181 men at high risk (HR) (2 or more risk factors within the range of eligibility for further study), but who declined participation; RS of 45 from 272 men excluded from further study due to exceptionally high risk; all of 85 exercise subjects (HR); all 82 controls (HR); and 36 men excluded from the exercise and control groups due to their high level of volitional activity. Subjects will be invited to the laboratory for a physical examination, resting electrocardiogram and blood pressure, fasting blood sample (for determination of total serum cholesterol, high density lipoprotein cholesterol, triglyceride, glucose, uric acid), anthropomorphic measurements (for determination of height, weight and percent body fat), pulmonary function tests, a progressive treadmill exercise test (to self-determined maximal work capacity or earlier endpoint at the subject's or administering physician's discretion), interview to determine habitual physical activity and change in activity over past several years, and a health opinion questionnaire to assess attitudes and behaviors regarding health practices. Longitudinal changes (with intergroup comparisons), morbidity, mortality, and associations among selected variables will be statistically analyzed.